Ceramic electronic component and method for manufacturing the same

ABSTRACT

A ceramic electronic component includes a ceramic element assembly and external electrodes. The external electrodes are disposed on the ceramic element assembly. The external electrodes include an underlying electrode layer and a first Cu plating film. The underlying electrode layer is disposed on the ceramic element assembly. The first Cu plating film is disposed on the underlying electrode layer. The underlying electrode layer includes a metal that is diffusible in Cu and a ceramic bonding material. The metal that is diffusible in Cu is diffused in at least a surface layer in the underlying electrode layer side of the first Cu plating film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a ceramic electronic component and amethod for manufacturing the same. In particular, the present inventionrelates to an embedded ceramic electronic component, which is arrangedto be embedded in a wiring board, and a method for manufacturing thesame.

2. Description of the Related Art

In recent years, along with miniaturization and thickness reduction ofelectronic apparatuses, e.g., cellular phones and portable musicplayers, wiring boards mounted on the electronic apparatuses have beenminiaturized.

Japanese Unexamined Patent Application Publication No. 2002-100875discloses a method for miniaturizing a wiring board in which a ceramicelectronic component is embedded inside of a wiring board and, inaddition, wiring to the ceramic electronic component is formed by usinga via hole disposed on the ceramic electronic component. According tothis method, it is not necessary to provide a region on the surface of awiring board for mounting a ceramic electronic component and, inaddition, it is not necessary to provide a region for wiring to theceramic electronic component separately from the region for mounting theceramic electronic component. Consequently, a wiring board including abuilt-in component can be miniaturized.

The via hole for connecting a ceramic electronic component is formed byusing, for example, a laser, e.g., a CO₂ laser. When the via hole isformed using the laser, the laser is applied directly to an externalelectrode of the electronic component. Therefore, it is preferable thatthe external electrode includes a Cu plating film to reflect the laserat a high reflectance. This is because if the reflectance of theexternal electrode with respect to the laser is low, the laserpenetrates to the inside of the ceramic electronic component and,thereby, the ceramic electronic component may be damaged.

Regarding the ceramic electronic component embedded in the inside of thewiring board, a reduction in profile has been extremely desirable fromthe viewpoint of thickness reduction of the wiring board.

For a method for reducing the profile of the ceramic electroniccomponent, it is preferable to fire an underlying electrode layerlocated immediately above a ceramic element assembly, among externalelectrodes, at the same time with the ceramic element assembly includinginternal electrodes, that is, to form through cofiring. This is becausethe maximum thickness of the underlying electrode layer can be reducedby the above-described method as compared to when the underlyingelectrode layer is formed by, for example, baking an electricallyconductive paste applied through dipping.

In this regard, when the underlying electrode layer is formed throughcofiring, it is necessary to increase the content of a ceramic bondingmaterial, e.g., a ceramic material, in the underlying electrode layer inorder to ensure high adhesion between the ceramic element assembly andthe underlying electrode layer. However, if the content of the ceramicbonding material in the underlying electrode layer is increased, thecontent of the metal component in the underlying electrode layer isdecreased. Consequently, the adhesion between the underlying electrodelayer and a plating layer disposed on the underlying electrode layer isreduced. Therefore, there is a problem in that the reliability of theelectronic component is degraded.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of thepresent invention provide a highly reliable ceramic electronic componentprovided with an external electrode including an underlying electrodelayer disposed on a ceramic element assembly and a Cu plating filmdisposed on the underlying electrode layer.

A ceramic electronic component according to a preferred embodiment ofthe present invention preferably includes a ceramic element assembly andan external electrode. The external electrode is disposed on the ceramicelement assembly. The external electrode preferably includes anunderlying electrode layer and a first Cu plating film, for example. Theunderlying electrode layer is disposed on the ceramic element assembly.The first Cu plating film is disposed on the underlying electrode layer.The underlying electrode layer preferably includes a metal that isdiffusible in Cu and a ceramic bonding material, for example. The metalthat is diffusible in Cu is diffused in at least a surface layer in theunderlying electrode layer side of the first Cu plating film.

According to another preferred embodiment of the present invention,grain boundaries are preferably present in the first Cu plating film.The metal that is diffusible in Cu is diffused along the grainboundaries of the first Cu plating film.

According to another preferred embodiment of the present invention, themetal that is diffusible in Cu is preferably diffused up to the surfaceopposite to the underlying electrode layer of the first Cu plating film.With this configuration, the adhesion between the first Cu plating filmand the underlying electrode layer is more effectively improved.

According to another preferred embodiment of the present invention, themetal that is diffusible in Cu is preferably at least one type of metalselected from the group consisting of Ni, Ag, Pd, and Au, for example.

According to another preferred embodiment of the present invention, theexternal electrode preferably further includes a second Cu plating filmdisposed on the first Cu plating film, and the metal that is diffusiblein Cu is not diffused in the second Cu plating film. With thisconfiguration, the second Cu plating film, in which the metal that isdiffusible in Cu is not diffused, is provided and, thereby, thereflectance at the external electrode with respect to the laser lightincident on the external electrode is further increased. Consequently,even when the laser light is applied to the external electrode, theceramic element assembly is not damaged. Therefore, the ceramicelectronic component is effectively used as an embedded ceramicelectronic component.

According to another preferred embodiment of the present invention, Cuis diffused in the underlying electrode layer from the first Cu platingfilm. In this case, the adhesion between the underlying electrode layerand the first Cu plating film can be more enhanced.

A method for manufacturing a ceramic electronic component according to apreferred embodiment of the present invention is a method formanufacturing a ceramic electronic component provided with a ceramicelement assembly and an external electrode disposed on the ceramicelement assembly. In the method for manufacturing a ceramic electroniccomponent according to this preferred embodiment of the presentinvention, an underlying electrode layer including a metal that isdiffusible in Cu and a ceramic bonding material are preferably formed onthe ceramic element assembly, and a first Cu plating film is formed onthe underlying electrode layer. Thereafter, the underlying electrodelayer and the first Cu plating film are heated, so as to form theexternal electrode by diffusing the metal that is diffusible in Cu intoat least the surface layer in the underlying electrode layer side of thefirst Cu plating film.

According to another preferred embodiment of the present invention, theexternal electrode is preferably formed by further forming a second Cuplating film on the first Cu plating film after the heating of theunderlying electrode layer and the first Cu plating film, so as todiffuse the metal that is diffusible in Cu into at least the surfacelayer in the underlying electrode layer side of the first Cu platingfilm. In this case, the second Cu plating film, in which the metal thatis diffusible in Cu is not diffused, is formed, so that the reflectanceat the external electrode with respect to the laser light incident onthe external electrode is increased and a ceramic electronic componentthat can be used as an embedded ceramic electronic component isproduced.

According to another preferred embodiment of the present invention, theexternal electrode is preferably formed by heating the underlyingelectrode layer and the first Cu plating film in a range of about 350°C. to about 800° C., for example, so as to diffuse the metal that isdiffusible in Cu into at least the surface layer in the underlyingelectrode layer side of the first Cu plating film. In this case, themetal that is diffusible in Cu is more effectively diffused.

In various preferred embodiments of the present invention, the metalthat is diffusible in Cu included in the underlying electrode layer isdiffused into at least the surface layer in the underlying electrodelayer side of the first Cu plating film. Consequently, the adhesionbetween the underlying electrode layer and the first Cu plating film isimproved. Therefore, the reliability of the ceramic electronic componentis effectively improved.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a ceramic electronic componentaccording to a first preferred embodiment of the present invention.

FIG. 2 is a schematic side view of the ceramic electronic componentaccording to the first preferred embodiment of the present invention.

FIG. 3 is a schematic sectional view along a line III-III shown in FIG.1.

FIG. 4 is a magnified schematic sectional view of a portion surroundedby a line IV shown in FIG. 3.

FIG. 5 is a magnified schematic sectional view of a part of a firstexternal electrode.

FIG. 6 is a schematic sectional view along a line VI-VI shown in FIG. 3.

FIG. 7 is a schematic plan view of a ceramic green sheet provided withan electrically conductive pattern.

FIG. 8 is a schematic plan view of a mother laminate.

FIG. 9 is a magnified schematic sectional view of a part of a ceramicelectronic component according to a second preferred embodiment of thepresent invention.

FIG. 10 is a schematic sectional view of a ceramic electronic componentaccording to a third preferred embodiment of the present invention.

FIG. 11 is a schematic sectional view of a ceramic electronic componentaccording to a fourth preferred embodiment of the present invention.

FIG. 12 is a schematic side view of a ceramic electronic componentaccording to a fifth preferred embodiment of the present invention.

FIG. 13 is a schematic sectional view of a ceramic electronic componentaccording to a sixth preferred embodiment of the present invention.

FIG. 14 is a schematic sectional view along the height direction H andthe length direction L of a ceramic electronic component according to aseventh preferred embodiment of the present invention.

FIG. 15 is a schematic sectional view along the height direction H andthe length direction L of a ceramic electronic component according tothe seventh preferred embodiment of the present invention.

FIG. 16 is a magnified schematic sectional view of a portion of a firstexternal electrode according to a modified example of a preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowwith reference to a ceramic electronic component shown in the drawingsas an example. However, the ceramic electronic component 1 is no morethan an example. The present invention is not limited to the ceramicelectronic component 1 and the manufacturing method thereof describedbelow.

First Preferred Embodiment

FIG. 1 is a schematic perspective view of a ceramic electronic componentaccording to a first preferred embodiment of the present invention. FIG.2 is a schematic side view of the ceramic electronic component accordingto the first preferred embodiment. FIG. 3 is a schematic sectional viewalong a line III-III shown in FIG. 1. FIG. 4 is a magnified schematicsectional view of a portion surrounded by a line IV shown in FIG. 3.FIG. 5 is a magnified schematic sectional view of a portion of a firstexternal electrode. FIG. 6 is a schematic sectional view along a lineVI-VI shown in FIG. 3.

The configuration of the ceramic electronic component 1 will bedescribed with reference to FIGS. 1 to 6.

As shown in FIGS. 1 to 3 and 6, the ceramic electronic component 1includes a ceramic element assembly 10. The ceramic element assembly 10is made of an appropriate ceramic material in accordance with thefunction of the ceramic electronic component 1. Specifically, when theceramic electronic component 1 is a capacitor, the ceramic elementassembly 10 is preferably made of a dielectric ceramic material.Specific examples of dielectric ceramic materials include BaTiO₃,CaTiO₃, SrTiO₃, and CaZrO₃. The ceramic element assembly 10 maypreferably include the above-described ceramic material as a primarycomponent, and secondary components, e.g., Mn compounds, Mg compounds,Si compounds, Fe compounds, Cr compounds, Co compounds, Ni compounds,and rare-earth compounds, may be added in accordance with thecharacteristics of a desired ceramic electronic component 1.

When the ceramic electronic component 1 is a ceramic piezoelectricelement, the ceramic element assembly 10 may preferably be made of apiezoelectric ceramic material. Specific examples of the piezoelectricceramic materials include lead zirconate titanate (PZT) based ceramicmaterials.

When the ceramic electronic component 1 is a thermistor element, theceramic element assembly 10 may preferably be made of a semiconductormaterial. Specific examples of the semiconductor ceramic materialsinclude spinel based ceramic materials.

When the ceramic electronic component 1 is an inductor element, theceramic element assembly 10 may preferably be made of a magnetic ceramicmaterial. Specific examples of the magnetic ceramic materials includeferrite ceramic materials.

The shape of the ceramic element assembly 10 is not specificallylimited. In the present preferred embodiment, the ceramic elementassembly 10 has a substantially rectangular parallelepiped shape. Asshown in FIGS. 1 to 3, the ceramic element assembly 10 includes firstand second principal surfaces 10 a and 10 b that extend in the lengthdirection L and the width direction W. As shown in FIGS. 1, 2, and 6,the ceramic element assembly 10 includes first and second side surfaces10 c and 10 d that extend in the height direction H and the lengthdirection L. Furthermore, as shown in FIGS. 2, 3, and 6, first andsecond end surfaces 10 e and 10 f that extend in the height direction Hand the width direction W are provided.

In the present specification, the term “a substantially rectangularparallelepiped shape” includes rectangular parallelepipeds havingchamfered or R-chamfered corner portions and ridge portions. That is,members having “a substantially rectangular parallelepiped shape” referto all members having first and second principal surfaces, first andsecond side surfaces, and first and second end surfaces. Furthermore,unevenness may be included on a portion of or all of the principalsurfaces, side surfaces, and end surfaces.

The dimensions of the ceramic element assembly 10 are not specificallylimited. However, the ceramic element assembly 10 is preferablylow-profile, so as to satisfy T≦W<L, (⅕)W≦T≦(½)W, and T≦0.3 mm, wherethe thickness dimension of the ceramic element assembly 10 is assumed tobe T, the length dimension is assumed to be L, and the width dimensionis assumed to be L. Specifically, it is preferable that 0.1 mm≦T 0.3 mm,0.4 mm≦L≦1 mm, and 0.2 mm≦W≦0.5 mm are satisfied.

As shown in FIGS. 3 and 6, inside of the ceramic element assembly 10, aplurality of substantially rectangular first and second internalelectrodes 11 and 12 are disposed alternately in the height direction Hat regular intervals. Each of the first and the second internalelectrodes is parallel or substantially parallel to the first and thesecond principal surfaces 10 a and 10 b. The first and the secondinternal electrodes 11 and 12 are opposed to each other with the ceramiclayer 10 g therebetween in the height direction H.

The thickness of the ceramic layer 10 g is not specifically limited. Thethickness of the ceramic layer 10 g may preferably be, for example,about 0.5 μm to about 10 μm. Likewise, the thickness of each of thefirst and the second internal electrodes is not specifically limited.The thickness of each of the first and the second internal electrodes 11and 12 may preferably be, for example, about 0.2 μm to about 2 μm.

The first and the second internal electrodes 11 and 12 may be made of anappropriate electrically conductive material. The first and the secondinternal electrodes 11 and 12 may preferably be made of, for example,metals, such as Ni, Cu, Ag, Pd, and Au, or alloys, such as a Ag—Pdalloy, including at least one of these metals.

As shown in FIGS. 1 to 3, first and second external electrodes 13 and 14are disposed on the surfaces of the ceramic element assembly 10. Thefirst external electrode 13 is electrically connected to the firstinternal electrode 11. The first external electrode 13 includes a firstportion 13 a disposed on the first principal surface 10 a, a secondportion 13 b disposed on the second principal surface 10 b, and a thirdportion 13 c disposed on a first end surface 10 e. In the presentpreferred embodiment, the first external electrode 13 is preferably notsubstantially disposed on the first and the second side surfaces 10 cand 10 d.

Meanwhile, the second external electrode 14 is electrically connected tothe second internal electrode 12. The second external electrode 14includes a first portion 14 a disposed on the first principal surface 10a, a second portion 14 b disposed on the second principal surface 10 b,and a third portion 14 c disposed on a second end surface 10 f. In thepresent preferred embodiment, the second external electrode 14 ispreferably not substantially disposed on the first and the second sidesurfaces 10 c and 10 d.

Next, the configurations of the first and the second external electrodes13 and 14 will be described. In this regard, in the present preferredembodiment, the first and second external electrodes 13 and 14preferably have substantially the same configuration. Therefore, theconfigurations of the first and second external electrodes 13 and 14will be described here with reference primarily to FIG. 4 showing aportion of the first external electrode 13.

As shown in FIG. 4, each of the first and the second external electrodes13 and 14 is preferably a laminate that includes an underlying electrodelayer 15 and first and second Cu plating films 16 and 17. The underlyingelectrode layer 15 is disposed on the ceramic element assembly 10. Thefirst Cu plating film 16 is disposed on the underlying electrode layer15. The second Cu plating film 17 is disposed on the first Cu platingfilm 16.

The underlying electrode layer 15 is preferably a layer to improve theadhesion strength between the first and the second external electrodes13 and 14 and the ceramic element assembly 10. Therefore, the underlyingelectrode layer 15 preferably has a composition that improves theadhesion strength between the underlying electrode layer 15 and theceramic element assembly 10 and, in addition, which improves theadhesion strength between the underlying electrode layer 15 and thefirst Cu plating film 16. Specifically, the underlying electrode layer15 preferably includes a metal that is diffusible in Cu and a ceramicbonding material, for example.

The content of the metal that is diffusible in Cu in the underlyingelectrode layer 15 is preferably within the range of, for example, about50 percent by volume to about 70 percent by volume. The content of theceramic bonding material in the underlying electrode layer 15 ispreferably within the range of, for example, about 30 percent by volumeto about 50 percent by volume.

The ceramic bonding material is preferably a component to improve theadhesion strength to the ceramic element assembly 10. The type of theceramic bonding material is selected such that, for example, when theceramic element assembly is fired at the same time with the underlyingelectrode layer, the shrinkage behavior of the ceramic element assemblyand the shrinkage behavior of the underlying electrode layer are similarto each other. It is preferable that the ceramic bonding materialincludes an element which is the primary component of the ceramicmaterial included in the ceramic element assembly 10. More preferably,the ceramic bonding material is the same ceramic material as that of theceramic material included as a primary component in the ceramic elementassembly 10.

The metal that is diffusible in Cu (hereafter may be referred to as“diffusible metal”) is preferably a component to improve the adhesionstrength to the first Cu plating film 16. In the present preferredembodiment, this diffusible metal is preferably diffused in at least thesurface layer in the underlying electrode layer 15 side of the first Cuplating film 16. Furthermore, Cu is diffused in the underlying electrodelayer 15 from the first Cu plating film 16. In the present preferredembodiment, high adhesion between the underlying electrode layer 15 andthe first Cu plating film 16 is achieved through this mutual diffusion.

More specifically, in the present preferred embodiment, grain boundariesare preferably present in the first Cu plating film 16, and thediffusible metal is diffused along the grain boundaries. Then, as shownin FIG. 5, a diffusion portion 16 a, in which the diffusible metal isdiffused, in the first Cu plating film 16 extends to the surfaceopposite to the underlying electrode layer 15 of the first Cu platingfilm 16. On the other hand, a diffusion portion 15 a, in which Cu isdiffused, is preferably present in the surface layer on the first Cuplating film 16 side of the underlying electrode layer 15.

The diffusion of the diffusible metal can be detected by polishing theside surface of the ceramic electronic component to the vicinity of thecenter in the W direction, so as to expose a cross-section parallel tothe opposite surface, treating the resulting cross-section by using afocused ion beam (FIB), and performing element mapping of wavelengthdispersive X-ray spectrometry (WDX).

The type of the diffusible metal is not specifically limited. Forexample, the diffusible metal may preferably be at least one metalselected from the group consisting of Ni, Ag, and Au. More preferably,Ni is used as the diffusible metal.

However, in the present preferred embodiment, the diffusible metal issubstantially not diffused in the second Cu plating film 17.Consequently, the second Cu plating film 17 is substantially made of Cu.

The maximum thickness of the underlying electrode layer 15 maypreferably be, for example, about 1 μm to about 20 μm. Preferably, themaximum thickness of the first Cu plating film 16 is, for example, about2 μm to about 6 μm. Preferably, the maximum thickness of the second Cuplating film 17 is, for example, about 3 μm to about 6 μm.

Next, an example of a method for manufacturing the ceramic electroniccomponent 1 according to a preferred embodiment of the present inventionwill be described.

A ceramic green sheet 20 (refer to FIG. 7) including a ceramic materialto define the ceramic element assembly 10 is prepared. As shown in FIG.7, an electrically conductive paste is applied to the resulting ceramicgreen sheet 20 and, thereby, an electrically conductive pattern 21 isformed. In this regard, application of the electrically conductive pastecan be performed by various printing methods, for example, a screenprinting method. The electrically conductive paste may include bindersand solvents used in the related art in addition to electricallyconductive fine particles.

A mother laminate 22 shown in FIG. 8 is produced by laminating aplurality of ceramic green sheets 20 provided with no electricallyconductive pattern 21, a ceramic green sheet 20 provided with anelectrically conductive pattern 21 having the shape corresponding to thefirst internal electrode 11 or the second internal electrode 12, and aplurality of ceramic green sheets 20 provided with no electricallyconductive pattern 21 in that order, and applying a hydrostatic pressurein the lamination direction.

An electrically conductive pattern 23 having the shape corresponding toportions defining the first and the second portions 13 a and 13 b of theunderlying electrode layer 15 of the first and the second externalelectrodes 13 and 14 is formed on the mother laminate 22 by anappropriate printing method, e.g., a screen printing method. In thisregard, the electrically conductive paste used for forming theelectrically conductive pattern 23 preferably includes the diffusiblemetal and the ceramic bonding material.

A plurality of green ceramic laminates are produced from the motherlaminate 22 by cutting the mother laminate 22 along virtual cut lines L.The cutting of the mother laminate 22 can be performed by dicing orforce cutting, for example.

After the green ceramic laminate is formed, chamfering or R-chamferingof corner portions and ridge portions of the green ceramic laminate andpolishing of the surface layer may be performed through barrel polishingor other suitable method, for example.

An electrically conductive paste is applied to both end surfaces of thegreen ceramic laminate and, thereby, an electrically conductive patternhaving a shape corresponding to portions defining the third portion 13 cof the underlying electrode layer 15 of the first and the secondexternal electrodes 13 and 14 is formed. This application of theelectrically conductive paste can be performed through, for example,dipping or screen printing. In this regard, the electrically conductivepaste used for forming the electrically conductive pattern preferablyincludes the diffusible metal and the ceramic bonding material.

The green ceramic laminate is fired. In the firing step, the underlyingelectrode layer 15 and the first and the second internal electrodes 11and 12 are fired at the same time (cofiring). The firing temperature canbe set appropriately in accordance with the types of the ceramicmaterial and the electrically conductive paste to be used. The firingtemperature can preferably be specified to be, for example, about 900°C. to about 1,300° C.

The first Cu plating film 16 is formed by applying Cu plating to theunderlying electrode layer 15. In the present preferred embodiment, theceramic laminate is subjected to a heat treatment thereafter, so as toheat the first Cu plating film 16 and the underlying electrode layer 15.The diffusible metal included in the underlying electrode layer 15 isdiffused into at least the surface layer in the underlying electrodelayer 15 side of the first Cu plating film 16 by this heating step.Along with that, Cu in the first Cu plating film 16 is diffused into atleast the surface layer in the first Cu plating film 16 side of theunderlying electrode layer 15. That is, mutual diffusion between theunderlying electrode layer 15 and the first Cu plating film 16 occurs.

In the heat treatment step of the first Cu plating film 16 and theunderlying electrode layer 15, the first Cu plating film 16 and theunderlying electrode layer 15 are preferably heated to about 350° C. toabout 800° C., and more preferably about 550° C. to about 650° C. If theheating temperature of the first Cu plating film 16 and the underlyingelectrode layer 15 is too low, diffusion does not reliably occur. On theother hand, if the heating temperature of the first Cu plating film 16and the underlying electrode layer 15 is too high, Cu included in thefirst Cu plating film 16 may be melted.

It is preferable that the above-described heat treatment step isperformed in an atmosphere of inert gas, such as nitrogen or argon, forexample. Consequently, oxidation of the first Cu plating film 16 iseffectively prevented.

Thereafter, the second Cu plating film 17 is formed by Cu plating on thefirst Cu plating film 16, so as to complete the ceramic electroniccomponent 1 shown in FIG. 1. As described above, in the presentpreferred embodiment, the second Cu plating film 17 is formed after thefirst Cu plating film 16 and the underlying electrode layer 15 areheat-treated. Consequently, the diffusible metal is diffused in thefirst Cu plating film 16, but the diffusible metal is not substantiallydiffused into the second Cu plating film 17. Therefore, the second Cuplating film 17 is formed substantially from Cu.

As described above, in the present preferred embodiment, the underlyingelectrode layer 15 is formed through cofiring. Consequently, the firstand the second portions 13 a, 14 a, 13 b, and 14 b of the first and thesecond external electrodes 13 and 14 can be formed so as to have smallthicknesses. Therefore, the thickness of the ceramic electroniccomponent 1 can be effectively reduced.

The underlying electrode layer 15 preferably includes the ceramicbonding material. Consequently, even when the underlying electrode layer15 is formed through cofiring, the adhesion between the underlyingelectrode layer 15 and the ceramic element assembly 10 is improved.

Furthermore, the underlying electrode layer 15 preferably includes themetal that is diffusible in Cu, and the metal that is diffusible in Cuis diffused in at least the surface layer in the underlying electrodelayer 15 side of the first Cu plating film 16. Consequently, theadhesion between the underlying electrode layer 15 and the first Cuplating film 16 is improved. In particular, when the metal that isdiffusible in Cu is diffused to the surface opposite to the underlyingelectrode layer 15 of the first Cu plating film 16, the adhesion betweenthe underlying electrode layer 15 and the first Cu plating film 16 isfurther improved.

In the present preferred embodiment, the second Cu plating film 17substantially formed from Cu is disposed on the first Cu plating film16. Consequently, even when the first and the second external electrodes13 and 14 are irradiated with laser light, the laser light is reflectedby the first and the second external electrodes 13 and 14 at a highreflectance. Therefore, even when the first and the second externalelectrodes and 14 are irradiated with the laser light, the ceramicelement assembly 10 is not damaged. That is, the ceramic electroniccomponent 1 according to the present preferred embodiment has highresistance to the laser light.

As described above, regarding the present preferred embodiment, thethickness of the ceramic electronic component 1 can be reduced, theadhesion between the ceramic element assembly 10, the underlyingelectrode layer 15, and the first Cu plating film 16 can be improved,and, in addition, the reflectance at the first and the second externalelectrodes 13 and 14 with respect to the laser light can be increased.Therefore, a highly reliable ceramic electronic component 1 according tothe present preferred embodiment can be effectively used as an embeddedceramic electronic component. When the ceramic electronic component 1according to the present preferred embodiment is used as the embeddedceramic electronic component, via holes may preferably be formed inportions on the first and the second external electrodes 13 and 14 ofthe ceramic electronic component by using the laser light withoutdamaging the ceramic electronic component 1.

In the present preferred embodiment, an example in which the ceramicelectronic component is provided with at least one pair of internalelectrodes and the first and the second external electrodes has beendescribed. However, preferred embodiments of the present invention arenot limited to this configuration. In preferred embodiments of thepresent invention, it is necessary that the ceramic electronic componentincludes at least one external electrode, and, for example, the internalelectrode is not necessarily included.

Other examples of preferred embodiments of the present invention will bedescribed below. In this regard, in the following explanations, theelements and components having substantially the same functions as thosein the above-described first preferred embodiment are not describedbelow.

Second Preferred Embodiment

FIG. 9 is a magnified schematic sectional view of a portion of a ceramicelectronic component according to a second preferred embodiment of thepresent invention.

In the first preferred embodiment, an example in which the first and thesecond external electrodes 13 and 14 include a laminate including theunderlying electrode layer 15 and the first and the second Cu platingfilms 16 and 17 was described. However, preferred embodiments of thepresent invention are not limited to this configuration. The externalelectrode is not specifically limited insofar as the underlyingelectrode layer and at least one Cu plating film laminated on theunderlying electrode layer are included.

For example, as shown in FIG. 9, each of the first and the secondexternal electrodes 13 and 14 may preferably include a laminateincluding an underlying electrode layer 15 and a first Cu plating film16 disposed on the underlying electrode layer 15. In this case, it ispreferable that the diffusible metal included in the underlyingelectrode layer 15 is not diffused to the surface opposite to theunderlying electrode layer 15 of the first Cu plating film 16. That is,it is preferable that the surface layer opposite to the underlyingelectrode layer 15 of the first Cu plating film 16 is substantially madeof Cu.

However, the diffusion is difficult to control in such a way that thediffusible metal is not diffused to the surface opposite to theunderlying electrode layer 15 of the first Cu plating film 16.Consequently, in order to ensure that the surface layers opposite to theceramic element assembly 10 of the first and the second externalelectrodes 13 and 14 are substantially made Cu, it is preferable toprovide a second Cu plating film 17.

Third Preferred Embodiment

FIG. 10 is a schematic sectional view of a ceramic electronic componentaccording to a third preferred embodiment of the present invention.

In the first preferred embodiment, the first and the second principalsurfaces 10 a and 10 b include a portion provided with the firstexternal electrode 13 or the second external electrode 14 and a portionnot provided with the first external electrode 13 nor the secondexternal electrode 14 that are arranged so as to be flush orsubstantially flush with each other. However, preferred embodiments ofthe present invention are not limited to this configuration. The firstand the second principal surfaces 10 a and 10 b may preferably include aportion provided with the first external electrode 13 or the secondexternal electrode 14 and a portion not provided with the first externalelectrode 13 or the second external electrode 14 that are notnecessarily arranged so as to be flush or substantially flush with eachother.

For example, as shown in FIG. 10, the first and the second principalsurfaces 10 a and 10 b preferably include a portion provided with thefirst external electrode 13 or the second external electrode 14 that isinward of the portion not provided with the first external electrode 13or the second external electrode 14 in the height direction H. In thiscase, the ceramic electronic component 1 has a lower profile.

Fourth Preferred Embodiment

FIG. 11 is a schematic sectional view of a ceramic electronic componentaccording to a fourth preferred embodiment of the present invention.

In the first preferred embodiment, an example in which each of the firstand the second external electrodes 13 and 14 is disposed on both thefirst and the second principal surfaces 10 a and 10 b is described.However, preferred embodiments of the present invention are not limitedto this configuration. Each of the first and the second externalelectrodes 13 and 14 may be provided on any portion of the surface ofthe ceramic element assembly 10.

For example, as shown in FIG. 11, each of the first and the secondexternal electrodes 13 and 14 may preferably be provided on only thesecond principal surface 10 b of the first and the second principalsurfaces 10 a and 10 b. When each of the first and the second externalelectrodes 13 and 14 is provided on at least one of the first and thesecond principal surfaces 10 a and 10 b, as described above, the ease ofmolding of the ceramic electronic component 1 is improved.

Fifth Preferred Embodiment

FIG. 12 is a schematic side view of a ceramic electronic componentaccording to a fifth preferred embodiment of the present invention.

In the first preferred embodiment, an example in which the first and thesecond external electrodes 13 and 14 are substantially not disposed onthe first and the second side surfaces 10 c and 10 d is described.However, as shown in FIG. 12, the first and the second externalelectrodes 13 and 14 may preferably also be provided on the first andthe second side surfaces 10 c and 10 d.

Sixth Preferred Embodiment

FIG. 13 is a schematic sectional view of a ceramic electronic componentaccording to a sixth preferred embodiment of the present invention.

In the first preferred embodiment, an example in which the first and thesecond internal electrodes 11 and 12 extend to the first end surface 10e or the second end surface 10 f and, in addition, the first and thesecond external electrodes 13 and 14 are provided on the first and thesecond end surfaces 10 e and 10 f, so as to electrically connect thefirst and the second internal electrodes 11 and 12 to the first externalelectrode 13 or the second external electrode 14 is described. However,preferred embodiments of the present invention are not limited to thisconfiguration.

For example, as shown in FIG. 13, via hole electrodes and 32 maypreferably be provided, and the first and the second internal electrodes11 and 12 may preferably extend to the first and the second principalsurfaces 10 a and 10 b, so as to be electrically connected to the firstand the second external electrodes 13 and 14 on the first and the secondprincipal surfaces 10 a and 10 b. In this case, it is sufficient thatthe first and the second external electrodes 13 and 14 are provided onat least one of the first and the second principal surfaces 10 a and 10b, and the first and the second external electrodes 13 and 14 are notnecessary provided on the first and the second side surfaces 10 c and 10d and the first and the second end surfaces 10 e and 10 f.

Seventh Preferred Embodiment

FIGS. 14 and 15 are schematic sectional views along the height directionH and the length direction L of a ceramic electronic component accordingto a seventh preferred embodiment of the present invention.

In the first preferred embodiment, an example in which the first and thesecond internal electrodes 11 and 12 are arranged in parallel to thefirst and the second principal surfaces 10 a and 10 b and, in addition,extend to the first and the second end surfaces 10 e and 10 f isdescribed. However, preferred embodiments of the present invention arenot limited to this configuration.

For example, as shown in FIGS. 14 and 15, the first and the secondinternal electrodes 11 and 12 may preferably be arranged in parallelalong the height direction H and the length direction L, and the firstand the second internal electrodes 11 and 12 may preferably be laminatedalong the width direction W. In this case, the first and the secondinternal electrodes 11 and 12 may preferably extend directly to at leastone of the first and the second principal surfaces 10 a and 10 b and beconnected directly to the first and the second external electrodes 13and led to at least one of the first and the second principal surfaces10 a and 10 b.

FIG. 16 is a magnified schematic sectional view of a portion of a firstexternal electrode according to a modified example of a preferredembodiment of the present invention.

In the first preferred embodiment, as shown in FIG. 5, an example inwhich the diffusion portion 16 a extends to the surface opposite to theunderlying electrode layer 15 of the first Cu plating film 16 wasdescribed. However, preferred embodiments of the present invention arenot limited to this configuration. For example, as shown in FIG. 16, thediffusion portion 16 a is not necessarily allowed to extend to thesurface opposite to the underlying electrode layer 15 of the first Cuplating film 16.

EXAMPLE 1

In the present example, a ceramic electronic component having the sameconfiguration as that of the ceramic electronic component 1 according tothe first preferred embodiment and functioning as a ceramic capacitorwas produced by the manufacturing method explained in the firstpreferred embodiment under the following condition.

Dimension of ceramic electronic component: about 1.0 mm×about 0.5mm×about 0.15 mm

Volume of ceramic electronic component: about 10 nF

Rated working voltage of ceramic electronic component: about 6.3 V

Primary component of ceramic material constituting ceramic elementassembly: BaTiO₃

Underlying electrode layer: about 50 percent by volume of Ni is includedas the metal that is diffusible in Cu.

Furthermore, about 50 percent by volume of ceramic bonding material isincluded.

Condition of formation of underlying electrode layer: firing at about1,200° C. for about 2 hours

Thickness of underlying electrode layer: about 5 μm

Thickness of first Cu plating film: about 4 μm

Thickness of second Cu plating film: about 4 μm

Condition of heat treatment to diffuse Ni into first Cu plating film:keeping at about 600° C. (maximum temperature) for about 10 minutes,total heat treatment time: about 1 hour, atmosphere: substantially inertgas atmosphere having oxygen concentration of about 10 ppm or less

The side surface of the ceramic electronic component produced asdescribed above was polished to the vicinity of the center in the Wdirection, a cross-section parallel to the opposite surface was exposed,the resulting cross-section was treated by using a focused ion beam(FIB), element mapping of wavelength dispersive X-ray spectrometry (WDX)was performed and, thereby, it was ascertained that Ni was diffused inthe first Cu plating film.

COMPARATIVE EXAMPLE 1

A ceramic electronic component was produced as in Example 1 describedabove except that the heat treatment to diffuse Ni into the first Cuplating film was not performed.

The ceramic electronic component produced as described above was cut toexpose the cross-section of the external electrode, and observation wasperformed by using an electron microscope. As a result, it wasascertained that Ni was not diffused in the first Cu plating film.

The second principal surface side of the ceramic electronic componentproduced in each of Example 1 and Comparative example 1 described abovewas bonded to a glass epoxy substrate by using an electricallyconductive adhesive. Thereafter, an adhesive tape (Cellotape (registeredtrademark) No. 252 produced by Sekisui Chemical Co., Ltd.) was stuck onthe first principal surface side of the ceramic electronic component,and was peeled off by pulling with a constant tension along the lengthdirection of the ceramic electronic component (180° peeling test).Subsequently, an observation whether peeling in the plating filmoccurred or not was performed by using an electron microscope. This testwas performed with respect to 100 samples each of Example 1 andComparative example 1 and the proportion of samples in which anoccurrence of peeling of plating film was observed was measured. As aresult, regarding Example 1, peeling was substantially not observed withrespect to every sample. On the other hand, regarding Comparativeexample 1, peeling was observed with respect to about 75% of samples.

As is clear from this result, the adhesion strength of the first Cuplating film is improved by diffusing the metal contained in theunderlying electrode layer into the first Cu plating film.

The second principal surface side of the ceramic electronic componentproduced in each of Example 1 and Comparative example 1 described abovewas bonded to a glass epoxy substrate by using an electricallyconductive adhesive. Thereafter, a load was applied at about 0.5 mm/secfrom both sides in the length direction of the ceramic electroniccomponent by using a loading jig until the external electrode was peeledoff.

As a result, regarding Comparative Example 1, peeling of the Cu platingfilm was observed, whereas regarding Example 1, peeling of the Cuplating film was substantially not observed even when the test wascontinued until the ceramic element assembly was broken.

As is clear from this result, the adhesion strength of the first Cuplating film is improved by diffusing the metal contained in theunderlying electrode layer into the first Cu plating film.

Regarding the ceramic electronic component produced in each of Example 1and Comparative example 1, 72 samples were mounted on glass epoxysubstrates by using eutectic solder. Thereafter, about 6.3 V of voltagewas applied to the sample for about 1,000 hours in a high-temperaturehigh-humidity bath at about 85° C. and a relative humidity of about 83%RH. A sample having an insulation resistance value after the load lifein humidity test of about 10 GΩ or less was counted as a defectivesample. As a result, regarding Example 1, among 72 samples, the sampleevaluated as a defective sample was substantially 0. On the other hand,regarding Comparative example 1, 30 samples were evaluated assubstantially defective samples among 72 samples.

As is clear from the results described above, the moisture resistance ofthe ceramic electronic component is improved by diffusing the metalcontained in the underlying electrode layer into the first Cu platingfilm.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A ceramic electronic component comprising: aceramic element assembly; and an external electrode disposed on theceramic element assembly; wherein the external electrode includes anunderlying electrode layer disposed on the ceramic element assembly anda first Cu plating film disposed on the underlying electrode layer; theunderlying electrode layer includes a metal that is diffusible in Cu anda ceramic bonding material; and the metal that is diffusible in Cu isdiffused into the first Cu plating film.
 2. The ceramic electroniccomponent according to claim 1, wherein grain boundaries are present inthe first Cu plating film, and the metal that is diffusible in Cu isdiffused along the grain boundaries of the first Cu plating film.
 3. Theceramic electronic component according to claim 1, wherein the metalthat is diffusible in Cu is diffused into the first Cu plating film soas to extend to a surface of the first Cu plating film opposite to asurface of the first Cu plating film that is adjacent to the underlyingelectrode layer.
 4. The ceramic electronic component according to claim1, wherein the metal that is diffusible in Cu is at least one metalselected from the group consisting of Ni, Ag, Pd, and Au.
 5. The ceramicelectronic component according to claim 1, wherein the externalelectrode further comprises a second Cu plating film disposed on thefirst Cu plating film, and the metal that is diffusible in Cu is notdiffused in the second Cu plating film.
 6. The ceramic electroniccomponent according to claim 1, wherein Cu is diffused in the underlyingelectrode layer from the first Cu plating film.